Control for suppressing occurrence of periodic disturbance is used in various controls such as positioning control with robot, shaft torque resonance suppression in dynamometer system, and vibration suppression of motor housing. In these applications, there is a demand for suppressing periodic disturbance accurately. A motor, for example, produces torque ripple in principle, and thereby causes various problems such as vibration, noise, adverse influence on ride quality and electrical and mechanical resonances. Especially, in the case of an interior PM motor spreading wide recently, there are produced cogging torque ripple and reluctance torque ripple compositely. A control method for suppressing this torque ripple is shown in Patent Document 1.
FIG. 13 is a block diagram showing a motor torque pulsation suppression system disclosed in Patent Document 1. This system is arranged to control the torque/speed of an electric motor with an inverter of a current vector control type. From motor drive currents iu, iv and iw sensed by a current sensor 12, and a rotor rotational angle θ of a motor 2, a coordinate transforming section 13 produces, by conversion, currents id and iq of a d-axis and q-axis orthogonal rotation coordinate system synchronous with the motor rotation coordinates. A current vector control section 11 of an inverter 1 controls the motor current by comparison between the converted d axis and q axis sensed currents and command values (id*, iq*). The rotor rotation angle ε is determined, from an encoder waveform abz produced by a rotational position sensor 3, by a speed phase sensing section 14, together with a speed ω.
A torque/id, iq converting section 15 converts a command torque Tref from a controller 5 and the motor rotation speed co into command d-axis and q-axis currents Id* and Iqo* in the rotation dq coordinate system in the vector control. A torque pulsation compensating current iqc* is superposed or added to the command q-axis current Iqo*, to determine a current vector control command. The controller 5 includes a torque ripple suppression control section or means 5A and a learning section or means 5B, and stores the compensating current required for suppressing the torque pulsation in the form of a Fourier coefficient table in a memory.
Then, a torque pulsation suppression control for suppressing torque pulsation in a feedforward manner is performed with the construction of a torque pulsation suppression system including a compensating table 16 shown in FIG. 14. Unlike FIG. 13, in the system of FIG. 14, controller 5 and torque meter 4 are omitted, the inverter 1 is provided with a compensating current producing section or means for suppressing torque pulsation, and torque command Tref* is applied directly to the compensating current producing section. As the compensating current generating section, there are provided an amplitude phase compensating current table 16 and a compensating current generating section 17.
The system of Patent Document 1 includes the upper controller to produce the control command and controls the controlled object or plant producing periodic disturbance, to suppress vibrations with the vibration suppressing compensating table obtained by a periodic disturbance observer. In other words, a torque pulsation component of the motor is extracted to perform the feedforward control to the controlled object, and the torque pulsation suppressing section or means is provided to determine the compensating current required to suppress the extracted torque pulsation component, and to suppress suppressing the torque pulsation by feed the compensating current back to the control apparatus of the controlled object. The system leans the torque pulsation compensating current at the time of torque pulsation suppressing control operation of the torque pulsation suppressing section, and values of the compensating current are collected in a table and stored in the control apparatus. At the time of the motor control operation, the system compensates for the torque pulsation in the feedforward manner with the compensating current read out from the table.
Patent Document 1: JP published patent document JP2011-50118A